Chris,
Have a look at these TMB eyepieces. I've bought and tested the entire line on refractors and fast Newts. In refractors they are all really good, except for the 6mm which has always been the weakest of the line.
For Newts, the pick of the crop are the 2.5mm, 4mm, 5mm, 7mm and the 8mm. The other focal lengths still do very well, though they show more field curvature than the ones listed above, and this is just splitting hairs - I tested these in an f/4 Newt which is really punishing on eyepieces. However, in an f/6 Newt there will be even less noticeable field curvature, if any.
I also compared these eyepieces with some high end eyepieces in order to get a more considered determination on their performance. The ones noted for use in a Newt are over all the best of the lot. These threw up an image every bit as good and sharp as the Pentax eyepieces I compared them to. These modest TMB's also had superior transmission to some other high end eyepieces.
And yes, Ebay is the best place to get them from:
https://www.ebay.com.au/sch/i.html?_...fLoc=2&_sop=15
They also have a wider AFOV than plossl eyepieces.
Those TV plossls are certainly good, but not your only option. The biggest problem that plossls eyepieces have is as the focal length gets smaller, the eye relief, or the distance you need to hold your eye from the eye-lens to look into it, becomes shorter and shorter, plus the eye-lens becomes smaller and smaller. You practically need to park your cornea onto the eye lens to look into a 4mm plossl. These TMB's all have the same generous eye relief across the entire line, and the same nice big eye lens. Below is a comparison picture of a 9mm plossl and the 9mm TMB.
A 9mm plossl is not an easy eyepiece to use, and it gets harder as the focal length gets shorter.
Alex.